The present invention relates to the field of surface cleaning devices and more particularly devices for automating the cleaning of printing screens.
It is deemed desirable to automate the in-process screen cleaning procedure associated with fabrication of thick-film hybrid microcircuits, including ceramic circuit cards. These microcircuits are composed of thick-film paste deposited by a screen printer using a stencil-like mask, or screen, which defines shapes of circuit components to be printed. Cleaning of the under side of the screen is required perodically during the printing process to assure print quality, and is accomplished manually by an operator who holds a polyfoam wiper in one hand, squirts xylene on it, and reaches under the screen to wipe the print area of the screen. A nitrogen gun is then used to dry excess xylene from the screen.
This manual process has the following disadvantages. The operator is exposed to solvent vapors and hand protection is required to minimize skin contact with the liquid solvent. Occasionally the operator will apply excessive force against the screen during the cleaning step which results in reduced screen life. Also manual screening is slower than desired and transfer of thick-film paste to the edges of the substrates occurs as a consequence of handling parts with the same gloves worn while cleaning the screen.